Cements have long been used in dentistry for a variety of purposes including the attachments of dental prosthesis such as crowns and bridges, posts and various other appliances to teeth. Unlike orthodontic appliances, such as orthodontic bands, braces or brackets, which are cemented or bonded primarily to the enamel portion of a tooth; crowns, bridges and dental posts are required to be cemented primarily to the dentin portion of a tooth. Bonding or cementing to dentin presents problems not common to bonding or cementing to tooth enamel. The problem is further aggravated with respect to cementing a dental post in a post hole formed in a tooth to be restored, as such post holes are generally enlarged root canals.
Cemented posts are required to withstand relatively large forces. The known procedures for preparing a post hole limits the options available for increasing post retention by mechanical interlocking. Therefore, post retention must be primarily achieved by friction and/or adhesive forces.
Heretofore, the selection of suitable prior art cements was strictly limited to self curing, two part cements which are required to be mixed shortly before application. The problem encountered with the use of the two part self curing cement required intimate mixing of the two components which limited the amount of working time for effecting the placement of the material before it sets. Further, a dentist had to precisely determine the ratio between the two components to be mixed, to assure proper reproducibility in the setting characteristics and properties of the cured cement, which is frequently difficult to achieve. Too little or too much of one or both of the components forming the mix could adversely effect the curing time, chemical properties and/or strength of the cured cement. The known light cured cements or materials, which provide the convenience of virtually unlimited working time, are not suitable for cementing a dental post in a post hole or placing a crown onto a tooth because of insufficient light penetration and related depth of cure requirements, necessary to achieve strong enough post or crown retention to resist the relatively large forces imparted upon the restored tooth.
The prior known methods of placing a dental post for effecting the replacement or rebuilding a tooth coronal structure generally required the mixing of two components of a self curing cement after the preparing of the post hole in a tooth. After the two components have been mixed, the mixture had to be delivered to the tooth by some means. Depending upon the nature of the mixed cement, it could be manually placed or syringed in the post hole and/or onto the post prior to insertion of the post into the post hole. As the cement was self curing after being mixed, time was of the essence to effect the placement of the post in the post hole and removal of the excess before the cement set. In the case of self curing resin cements, most required the added step of etching and/or applying a bonding agent into the post hole before the self curing cement components were mixed and placed. Thus, the additional step of etching and/or covering the walls of the preparation with a suitable bonding agent was required. The conventional resin cements used for cementing or bonding dental prosthesis such as bands, brackets and braces to the enamel portion of the tooth are not best suitable for cementing dental posts to the dentin portion of a tooth.